Lamp Base to Socket Contact
Good electrical contact between the lamp base and the socket is essential. Check to see if the lamp is loose in the socket or if the base is distorted so that the lamp will not seat properly.
Faulty Socket or Wiring
Check socket for loose contacts, poor connections, or broken wiring.
High pressure sodium and low-wattage metal halide lamps require a starter that provides a high-voltage pulse to start the lamp. The socket must be capable of withstanding the pulse without arcing. A pulse-rated socket is required.
Lamp Operation Position
Some metal halide lamps are restricted to an optimum operating position. For example, base-up to horizontal are so identified in the lamp etch. The proper lamp must be used for the given operating position. Other metal halide lamps, which are designed for horizontal operation only, have a special position-oriented base which must be used with a matching socket to assure proper arc tube orientation. Otherwise, the lamp will produce low light output and fail early.
Lamp Damage Due to Handling or Shipping
Damage to the outer bulb from handling or shipping may cause a crack in the glass, broken tubes or wires, or loose parts in the lamp. Air entering the bulb will oxidize the metal parts and result in short lamp life.
High pressure sodium lamps contain a getter-the dark material in the outer bulb, near the base. The getter absorbs residual oxygen from the lamp-making process. If air has entered the bulb, the getter will be used up. It will appear white or be gone.
Lamp Damage Due to Overwattage or Overcurrent Operation
Overwattage or overcurrent operation will result in short lamp life. Signs include a swollen, bulged or blackened arc tube, melted wires or ribbons inside the lamp, and a discolored outer bulb.